Epitaxial　thin　films　composed　of　perovskite　and　brownmillerite　oxides　have　received　increasing　attention　because　of　the　novel　phenomena　found　in　these　systems.　Herein,　the　atomic　and　electronic　structures　of　the　La0.75Sr0.25MnO3/SrCoO2.5　interface　have　been　studied　using　first-principles　calculations.　From　the　perspective　of　polarity　compensation,　three　types　of　possible　interface　models　are　constructed,　which　have　different　interface　terminations　or　orientation　relationship.　In　the　model　where　the　[100]　direction　of　SrCoO2.5　is　parallel　to　the　interface,　the　interface　is　polar.　The　way　to　compensate　polarity　is　atomic　reconstruction.　For　the　model　with　the　[100]　direction　of　SrCoO2.5　perpendicular　to　the　interface,　there　are　two　possible　interface　terminations.　One　is　nonpolar.　The　other　is　polar,　but　its　polarity　can　be　compensated　by　electronic　redistribution,　i.e.,　the　valence　change　of　Mn　from　+3　to　+4　at　the　interface,　as　consistently　revealed　by　the　change　of　the　bond　valence　sums　and　magnetic　moments　of　Mn　ions.　For　this　model　with　electronic　redistribution,　accompanied　by　the　valence　change,　the　MnO6　octahedra　near　the　interface　have　the　largest　distortion　compared　with　the　other　two　models.　The　density　of　states　around　Fermi　level　and　the　magnetic　coupling　across　the　interface　are　also　discussed.